This invention relates generally to means for monitoring the rotation of a shaft or other rotateable member and more particularly to a magnetic device adapted to be mounted for rotation with the member and cooperable with responsive means for providing signals in accordance with the rotation of the shaft or member.
Heretofore, a number of different suggestions have been made for detecting or monitoring the rotation of a shaft or member. Certain of such means utilize structures including a perforated disc with a photoelectric sensing element on one side and a light source on the other side. As the disc rotates, light shining through the perforations provides a plurality of signals. Another previously suggested approach contemplates the use of a reed switch actuated by a single magnetic member rotateable with the shaft to provide the desired signals, but this approach obtains only one signal for each shaft rotation whereby difficulties may be encountered in monitoring relatively slower devices. Still another suggestion is to provide a unit with a plurality of separate permanent magnets positioned around the shaft or rotateable member, but this approach requires a relatively complicated and expensive structure.
While features of the present invention may be utilized for monitoring shafts or rotateable members in a variety of types of machines or apparatus, it is contemplated that the invention will be especially suitable for use in agricultural equipment. Such equipment is subjected to rough use in a hard environment so that maintenance or replacement of parts of monitors of the type contemplated herein may be required. Since a malfunction may occur at any time and particularly in the field, it is desirable that the monitoring unit and parts thereof be constructed so that replacement, maintenance or adjustment can be accomplished with a minimum of specialized training and skill and preferably by the operator.